Drawing FIG. 1 depicts a typical prior art transducer in the form of a loudspeaker. The speaker has a magnet and a pole piece and a metal speaker frame or basket. The metal frame is connected directly to the magnet and pole piece via a metal top plate thereby creating an electrical conduction between the metal frame and magnet and pole piece.
An enlarged slot is provided between the upper portion of the combined pole piece and magnet providing a close tolerance co-axial space for movement of a voice coil and its support form within the slot. Voltage often in the range of 240 volts AC or more is present on the windings of a voice coil depending on amplifier construction.
A typical rather stiff speaker cone is fixedly secured at its widest circumference to a flexible suspension member which is fixedly attached at its smallest end to the voice coil form and spider.
The problem occurring with this configuration is that an off center voice coil position can cause the windings of the voice coil to rub against the magnet or pole piece wearing off the insulation on the coil wires and shorting the line voltage on the coil to the magnet and pole piece and hence to the metal frame surrounding the speaker cone. Obviously, this places line voltage where it can come in contact with a person touching the metal frame of the speaker and can be lethal if that person should simultaneously come in contact with ground potential.
It would be of great advantage to eliminate this potential hazard by providing an inexpensive way to isolate the high voltage from the speaker frame in the event of a short circuit of the voice coil winding to the metal frame.
There has not been a satisfactory economically inexpensive means or method to isolate the high voltage from becoming a potential hazard in the absence of an isolation transformer until the present invention.